1. Field of the Invention
The present invention relates to an injection apparatus both for positive and negative ions which can be applied on a proton accelerator, a various ion accelerator and the like.
2. Description of Related Art
In conventional ion accelerators including, for instance, a synchrotron, which are used for accelerating positive ions or negative ions, are employed to the injection apparatus which are arranged in widely different forms in response to either ions to be accelerated positive or negative.
For example, as for the injection apparatus used for the proton accelerator, a multi-turn injection system based on charge exchange by negative hydrogen ions, is generally adopted, as exemplified in FIG. 3. A negative ion injection apparatus as shown in FIG. 3 is formed by arranging bump magnets 11, 12, 13 and 14 in turn on a circulating orbit, intermediate ones 12 and 13 of which are arranged so as to make a determined offset against end ones 11 and 14 and further between intermediate ones 12 and 13 a carbon film 15 is fixedly disposed.
As shown in FIG. 4 which indicates a cross-section A--A in FIG. 3, the bump magnet 12 is formed of a magnet 12a having a C-shaped longitudinal cross-section, inside of which conductors 12b and 12c provided for forming single turn exciting coils are arranged in such a way that a center of a circulation orbit and a beam injection point are positioned between these conductors 12b and 12c.
In the above exemplified conventional negative ion injection apparatus, an orbit of a negative ion beam, for instance, H- ion beam which is injected into the bump magnet 12 at a determined angle is deflected, upon the injection of negative ion, that is, upon the charge conversion multiplex injection, by the bump magnetic field formed in the bump magnet 12, substantially in parallel with the circulation orbit center as shown in FIG. 3, and then, after passed through the bump magnet 12, electrons are separated from the negative ion beam by the carbon film 15, so as to be converted into a positive ion beam. This positive ion beam gets on the circulation orbit through bump magnets 13 and 14, and then, during the subsequent circulation, is injected into the bump magnet 12 along the orbit which is deflected through the bump magnet 11 as shown in FIG. 3. The orbit of this positive ion beam is deflected by the aforesaid bump magnetic field in an opposite direction to that in the case of the negative ion beam, and, as a result, flows into the negative ion beam.
In this connection, according to the function of the bump magnet 11 to 14, it is arranged that the orbit is shifted in such a way as the injected ion beam is passed through the carbon film 15 only upon the negative ion injection.
On the other hand, as for the injection apparatus used for the positive ion accelerator, a circulation orbit shift system is adopted in general, as exemplified in FIG. 5. A positive ion injection apparatus as shown in FIG. 5 is formed by arranging a septum magnet 21 afforded with a determined offset against the circulation orbit center together with bump magnets as not shown in FIG. 5 in both of upper and down streams in the circulation orbit direction.
As shown in FIG. 6 which indicates a crosssection B--B in FIG. 5, the septum magnet 21 is formed of a magnet 21a having a U-shaped longitudinal crosssection, inside of which conductor 21b and 21c provided for forming single turn exciting coils are arranged in such a way that a beam injection point is positioned between these conductors 21b and 21c and outside of which a center of a circulation orbit is positioned.
In the above exemplified conventional positive ion injection apparatus, an orbit of a positive ion beam which is injected into the septum magnet 21 at a determined angle is deflected, upon the injection of positive ion, that is, upon the circulation orbit shift multiplex injection, substantially in parallel with the circulation orbit center as shown in FIG. 5, by the fact that the circulation orbit which is shifted by a bump magnet as not shown in FIG. 5 is temporarily passed through a septum magnetic field formed in the septum magnet 21, and then gets on the circulation orbit through the aforesaid bump magnet as not shown in FIG. 5.
In the above exemplified conventional ion injection apparatus as shown in FIG. 4 which is used for the proton accelerator, the charge exchange injection system based on negative ions is adopted. In this charge exchange injection system based on negative ions, it is possible to efficiently inject the ion beam into the circulation orbit. However, in the case that particles being heavier than He ion are injected, upon the charge exchange effected by making negative ions to impinge with the carbon film after the injection, the decrease of injection efficiency is caused because the ratio between the charge and the mass is not constant compared from the case of proton. So that, this charge exchange injection system based on negative ions cannot be applied on the case that heavy ions are injected. In order to facilitate the injection of positive ions being heavier than He ion in the circular accelerators including the proton accelerator, it is required to further provide an additional injection apparatus, for instance, the positive ion injection apparatus as shown in FIG. 6, which comprises the septum magnet for deflecting the orbit of the injected beam substantially in parallel with the circulation orbit, as well as the bump magnet for parallelly shifting the circulation orbit in upper and lower streams of the above septum magnet, so as to inject the beam in parallel with the circulation orbit through the septum magnet during the circulation orbit is shifted.
As described above, the negative ion injection and the positive ion injection have been conventionally realized respectively by different injection apparatus. Accordingly, in the case either negative ions or positive ions are injected and accelerated through the same accelerator, it has been conventionally required to provide the aforesaid two kinds of injection apparatus, and to change these injection apparatus from each other, each time the kind of the beam to be injected is changed. For changing the injection apparatus which is set up in vacuum together with the accelerator, it is necessary to break the vacuum situation. So that, the work for this change becomes largely scaled and further requires a working term longer than three weeks. As a result, an enormous working cost is necessary for it, as well as the restriction is brought into the application of the accelerator.